1. Field
The present invention is related to a power generation device which uses a metabolic reaction of a microbe. In particular, the present invention is related to a microbial power generation device which extracts the reducing power obtained when a microbe decomposes an organic substrate by oxidation as electrical energy.
2. Description of the Related Art
In recent years, the requirements for a power generation method that takes into account the global environment are increasing and the technological development of microbial power generation is progressing. Microbial power generation is a method of generating power by extracting the reducing power obtained when microbes assimilate organic substances as electrical energy.
Generally, in microbial power generation, microbes and organic substances which are assimilated by the microbes coexist within an anode chamber arranged with an anode. In addition, depending on the case, an electron transport substances or materials (electron mediator) are added into the anode and/or the anode chamber and receives the electrons which are generated when the microbes oxidize the organic substances, and passes the electrons to the anode. The anode is electrically conductive with a cathode through an external circuit, and the electrons which are passed to the anode move to the cathode and are passed to an electron acceptor through the cathode. A current flows between the cathodes and the anodes due to the movement of the electrons and electrical energy is obtained.
In microbial power generation, because an electron mediator directly extracts electrons from microbes the theoretical energy conversion efficiency is high. However, the actual energy conversion efficiency is low and therefore improvements in power generation rates are required. Thus, various examinations and developments are being undertaken with respect to the material and structure of electrodes, the type of electron mediator and the selection of the species of microbe in order to increase power generation rates (for example, refer to Japanese Laid Open Patent 2007-95470, and P. Aelterman et al., 2006 ENVIRONMENTAL SCIENCE & TECHNOLOGY, Vol. 40, No. 10, pp. 3388-3394). In Japanese Laid Open Patent 2007-95470, a power generation rate is improved by using an anode which is introduced with a functional group binding chemically with an electron mediator.
In Japanese Laid Open Patent 2007-95470, electrons which are produced when microbes oxidize an electron donor (organic substances) are extracted to an anode via an electron mediator. As a result, it is necessary to supply not only the electron donor to an anode chamber but also the electron mediator. In addition, because an additional process which introduces a functional group to the anode is necessary the manufacturing costs of the anode increase. Consequently, a new technology for improving the power generation rate which does not lead to an increase in costs is being demanded. In addition, adverse effects on the microbial reaction may be generated depending on the type of mediator.